Evrim Yazgin
Cosmos science journalist
Get excited. The world’s most powerful space telescope ever is releasing its first full colour photographs of the universe.
Six months after reaching its final destination in orbit around the Sun, more than one million kilometres above the Earth, the James Webb Space Telescope (JWST) is sending back its first full-colour images.
In April, JWST’s instruments were aligned. In May, we received the first calibration images showing the unprecedented quality with which James Webb will help us see the cosmos for the next 20 years.
Now, the big one. The only photo dump worth staying up all night for – 10-20 photographs in full colour. And it arrived at 12:30am AEST on Wednesday, July 13.
Included in the images are the furthest look into the early universe seen so far, exoplanet atmospheres, and photographs made from 2,000 different infrared colours.
Emotions run high as images reveal universe’s secrets
The few scientists who have had a sneak peek at the images have said they were left on the verge of tears. “It’s an emotional moment when you see nature suddenly releasing some of its secrets,” says Thomas Zurbuchen, associate administrator for NASA science missions. “It’s not an image. It’s a new worldview.
“Our goals for Webb’s first images and data are both to showcase the telescope’s powerful instruments and to preview the science mission to come,” says astronomer Klaus Pontoppidan, Webb project scientist at the Space Telescope Science Institute (STScI) in the US. “They are sure to deliver a long-awaited ‘wow’ for astronomers and the public.”
“I feel very privileged to be a part of it,” says Alyssa Pagan, a science visuals developer at STScI. “Typically, the process from raw telescope data to final, clean image that communicates scientific information about the universe can take anywhere from weeks to a month.”
“What I have seen moved me, as a scientist, as an engineer, and as a human being,” says NASA deputy administrator Pam Melroy.
“There is already some amazing science in the can, and some others are yet to be taken as we go forward. We are in the middle of getting the history-making data down,” adds Zurbuchen.
Webb’s eyes into the skies
James Webb is equipped with four powerful optical instruments. The four tools collect data from the cosmos in specific ranges of electromagnetic radiation (light) wavelengths and particular imaging types.
- Mid-Infrared Instrument (MIRI) provides imaging and spectroscopic observation for radiation with wavelengths from 4.9 to 28.8 micrometres.
- Near Infrared Camera (NIRCam) is focused on wavelengths of light from 0.6 to 5.0 micrometres. It is also used for JWST mirror alignment.
- Near Infrared Imager and Slitless Spectrograph (NIRISS) observes at wavelengths between 0.6 and 5.0 micrometres.
- Near Infrared Spectrograph (NIRSpec) provides spectroscopy from 0.6–5.3 micrometres.
The infrared spectrum of light occurs just next to the visible spectrum (380 to 700 nanometres) and is essentially heat.
Infrared radiation detection is important for a couple of reasons.
Much of the universe is hidden behind veils of gas and other particles in our own Milky Way galaxy. Strewn between galaxies is what is called the intergalactic medium. This stuff masks the magnificent structures behind them, obscuring from view visible light from whole areas of the universe.
Infrared light, however, pierces through this shroud to reveal the heat-giving structures like stars and nebulae behind.
It already takes massive amounts of time for the light from these distant objects to reach our observatories on and around Earth – billions of years. As the universe expands, the galaxies and stars spread even further apart.
Due to the universe’s expansion, the electromagnetic waves coming from a source like a far-away galaxy stretch and become longer.
Known as Doppler shift, this is the same effect you hear when sound waves are produced, for example, by an ambulance speeding passed you. As the ambulance moves further away, its siren lowers in pitch as the sound waves have further to travel. Their wavelength increases, causing their pitch to drop.
It is the same with light, except instead of hearing a lowering in pitch, we see a “reddening”. Visible light from distant objects “reddens” to the point where, by the time it reaches Earth, the electromagnetic radiation is no longer visible, but part of the infrared (below red) part of the spectrum can be detected.
How are full-colour images produced?
But, given the data collected by JWST is not in the form of the visible colour spectrum we know, how come the released images are in full colour? We can’t see infrared colours.
Well, the colour isn’t applied randomly. Certain colours may be highlighted to draw attention to specific features for scientific purposes, but the process of turning infrared observations into full-colour images flows from the Doppler effect.
Much like transposing music to a different key or shifting whale song into the audible range of human hearing to listen to the cetacean music, electromagnetic radiation can be shifted back up.
Knowing the rate at which the universe is expanding, plus the distance between Earth and the source of light, astronomers can “unshift” the red-shifted light coming from the object. Hence, we get an optical picture of what the object looks like (or looked like billions of years ago when the light left the object’s surface).
What are we looking at?
After outlining the process above, not to mention the fact that JWST is looking at light that has travelled billions of lightyears, you’ll appreciate that producing the first James Webb images is more complicated than a smartphone camera’s point-and-click.
“When you get the data down, they don’t look anything like a beautiful colour image. They hardly look like anything at all,” says Klaus Pontoppidan. “It’s only when you know, as an expert, what to look for that you can appreciate them.”
Part of the fun of having the most powerful telescope ever is we’re not even sure what will be revealed.
“Of course, there are things we are expecting and hoping to see, but with a new telescope and this new high-resolution infrared data, we just won’t know until we see it,” says STScI lead science visuals developer Joseph DePasquale.
But the first images are sure to contain some things. This includes the farthest image taken.
Among the list of objects at which the James Webb Space Telescope pointed to give us the first batch of full-colour photos are:
- Carina Nebula: One of the largest and brightest nebulae in the sky. It is approximately 7,600 light-years away in the southern constellation Carina. The Nebula is home to many stars several times larger than the Sun.
- WASP-96 b: This one’s not a photo, but a colour spectrum of a giant gaseous planet outside our solar system. Located nearly 1150 light-years from Earth, the planet orbits its star every 3.4 days. It’s about half Jupiter’s mass and its discovery was announced in 2014.
- Southern Ring Nebula: The Southern Ring, or “Eight-Burst” nebula, is a planetary nebula – an expanding cloud of gas surrounding a dying star. It is nearly half a lightyear in diameter and is approximately 2,000 light years away.
- Stephan’s Quintet: About 290 million light-years away, located in the Pegasus constellation. Four of the five galaxies within the quintet are locked in a cosmic dance of repeated close encounters.
- SMACS 0723: Massive foreground galaxy clusters magnify and distort the light of objects behind them, giving a deep field view into extremely distant and faint galaxies.
“Webb is nothing short of a real scientific feat. One of those images on July 12 is the deepest image of our universe that has ever been taken,” says NASA administrator Bill Nelson.
Because light takes billions of years to travel from distant objects to us, we are essentially looking at the past.
“If you think about that, this is farther than humanity has ever looked before and we are only beginning to understand what Webb can and will do.
About 20 years ago, the Hubble Space Telescope’s Ultra Deep Field survey captured the oldest visible galaxies dating back to around 800 million years after the Big Bang, which is estimated to have occurred around 13.8 billion years ago. So, we’re talking old.
NASA has also presented the first study by JWST of the atmosphere of a planet outside the solar system, the hot gas giant known as WASP-96 b.
On June 27, NASA announced that NIRISS concluded its preparations and will reveal more than 2,000 infrared colours. This mode will be specifically used for examining the atmospheres of exoplanets.
As the planets orbit their stars, they absorb some of the stars’ light. The absorption of specific wavelengths relates to the presence of particular molecules in the extra-solar planets’ atmospheres. Hence, as a planet passes in front of its star, astronomers can use the NIRISS tool to determine the chemical makeup of these alien airs – and potentially find those on which we can breathe and/or find extra-terrestrial life.
The Single Object Slitless Spectroscopy capability of the NIRISS instrument is a specialised prism assembly that disperses light to create three distinctive infrared spectra to reveal the 2,000 hues in a single observation.
“I’m so excited and thrilled to think that we’ve finally reached the end of this two-decade-long journey of Canada’s contribution to the mission,” says René Doyon, principal investigator for NIRISS, as well as Webb’s Fine Guidance Sensor at the University of Montreal. “All four NIRISS modes are not only ready, but the instrument as a whole is performing significantly better than we predicted. I am pinching myself at the thought that we are just days away from the start of science operations, and in particular from NIRISS probing its first exoplanet atmospheres.”
Nelson adds: “It’s going to explore objects in the solar system and exoplanets orbiting other stars giving us clues as to whether, potentially, their atmospheres are similar to our own, and may answer some questions that we have. Where do we come from? What more is out there? Who are we? And, of course, it’s going to answer some questions that we haven’t thought to ask yet.”
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